bytebuddy能否拦截方法调用并使其调用第二个对象的私有方法？

Question

给定一个类a，使用一个公共方法覆盖（B that，C arg），第二个类B，使用一个私有方法调用（C arg）。有没有可能用bytebuddy生成一个子类，该子类将调用私有方法callMe（C arg），从实现的overrideMe（B that，C arg）？这基本上会模拟JVM反射生成的MethodAccessor，它正是这样做的。

目前，我正在尝试使用以下方法调用：

Method callMeHandler = B.class.getDeclaredMethod("callMe");
callMeHandler.setAccessible(true);
MethodCall methodCall = MethodCall.invoke(callMeHandler).onArgument(0);
if(callMeHandler.getParameterCount() == 1)
    methodCall = methodCall.withArgument(1);

Composable coercedMethodCall = methodCall
           .withAssigner(ReferenceTypeAwareAssigner.INSTANCE, Typing.DYNAMIC);

String className = callMeHandler.getDeclaringClass().getName()
       + "$_generatedAccessor$" + callMeHandler.getName()
       + "$" + accessorCounter.getAndIncrement();

new ByteBuddy().subclass(GeneratableHandlerInvocation.class)
               .name(className)
               .method(ElementMatchers.named("invoke"))
               .intercept(Advice.to(GeneratableHandlerInvocation.class)
                                .wrap(coercedMethodCall))
               .make()
               .load(callMeHandler.getDeclaringClass().getClassLoader())
               .getLoaded()
               .newInstance();

，但它抱怨

java.lang.IllegalStateException: Cannot invoke private void com.mycompany.secret.B.callMe() virtually
    at net.bytebuddy.implementation.MethodCall$MethodInvoker$ForVirtualInvocation$WithImplicitType.invoke(MethodCall.java:2124)
    at net.bytebuddy.implementation.MethodCall$Appender.apply(MethodCall.java:2400)
    at net.bytebuddy.asm.Advice$Appender$EmulatingMethodVisitor.resolve(Advice.java:7156)
    at net.bytebuddy.asm.Advice$Appender.apply(Advice.java:7109)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyCode(TypeWriter.java:614)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyBody(TypeWriter.java:603)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod.apply(TypeWriter.java:521)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:4102)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:1612)
    at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:174)
    at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:155)
    at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:2560)
    at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$Delegator.make(DynamicType.java:2662)
    at com.mycompany.secret.Main.defineTheSpecialClass(Main.java:190)

Answer 1

不，这是不可能的。JVM的字节码验证器禁止它。因此，Byte Buddy首先不允许您创建这样的方法调用。

如果您想更改一个类并允许这样的调用，请查看Byte Buddy的代理API和允许您更改现有代码的Advice类。